func anat 2 Flashcards
(126 cards)
Newton’s 1st Law
Bodies in motion
tend to remain in motion.
Bodies at rest tend to
remain at rest
Force
An action or influence on
an object that produces or
prevents motion, or has a
tendency to do so
Internal force
Muscles and other
anatomical structures
External force
weights, braces,
therapist’s hands, gravity,
etc
objects movement (force) depends on…
Amount of force
Inertia
Mass
Friction
Qualities of Force
magnitude of direction
what represents qualities of force
vector (arrow)
Resultant Force
two or more forces acting on an object, the resultant
force, and therefore the movement of the object, is a
combination of the two forces.
concurrent force
creates resultant force
ex) gluteus medias
ex) Maureen and i pulling a rope to propel Brooklyn forward.
formula for finding torque
torque = force x length of lever arm
longer moment arm =
more torque
torque
force that produces rotation of a body segment around a relatively fixed axis.
Torque in Physiology…
If the biceps muscle pulls with 12 lbs of force, and
the insertion of the muscle is 2 inches from the axis
of rotation, then the torque produced is:
1/6 ft x 12 lbs = 2 ft*lbs
Lever arm: 2 inches or 1/6 ft
Force: 12 pounds
axis=elbow
biceps flexion=force
resistance=weight of forearm and hand
Muscles that pull superiorly or laterally to the axis of rotation…
Muscles that pull inferiorly or medially to the axis of rotation..
Muscles that rotate body part internally…
Muscles that rotate body part externally…
force couples
muscles act together to produce rotational movement by acting in equal and opposite directions, resulting in a single rotational movement
ex) screwing on a jar/water bottle lid
force couples in the shoulder…raising your arm
as you abduct your arm the deltoid generates an outward and upward force on the humerus. the infraspinatus, teres minor, and subscapularis counter this by generating a downward and inward force to keep the humerus in socket and stabilize the joint.
Simple Machines
pulleys and levers
pulley
change the direction of a force.
With a simple pulley, you pull
down, and the object goes up.
patella pulley
The patella, or knee cap,
acts as a pulley for the
muscle of the knee.
It changes the direction of
the pull of the muscle…
BUT, it also adds a
mechanical advantage to
the muscle.
It increases the lever arm of the
extensor mechanism, and thus
increase quadriceps strength by
up to 33–50%.
It increases the moment
arm, which in turn
increases torque
production
lever
increase force or
torque.
moment arm
the perpendicular distance from an axis to the line of action of a force